In the "Solar Sprint" activity, students design, test, and race a solar-powered car built with Legos. The use of ratios is incorporated to simulate the actual work of scientists and engineers. This method encourages fourth-grade students to think about multiple variables and stimulates their curiosity when an activity doesn't come out as predicted. This activity also integrates the study of electricity and motion into a discussion of alternative energy sources and means of transportation. (Contains 1 figure, 1 resource and 1 online resource.)